Fail safe redundant drive shaft apparatus including electrically operative failure detection means

Abstract

Drive shaft apparatus includes driving and driven members and primary torque transmitting means coupling the members. Redundant torque transmitting means is rendered operative for coupling said members in the event of a failure of the primary coupling means and a failure detector including electrical circuitry arranged with the redundant coupling means detects the operation thereof and provides a corresponding indication.

What is claimed is: 
     
       1. Drive shaft apparatus, comprising: a drive shaft having driving and driven members;   primary torque transmitting means coupling the driving and driven members;   redundant torque transmitting means coupled to the primary torque transmitting means and rendered operative upon a failure of the primary torque transmitting means for coupling the driving and driven members, the redundant torque transmitting means including a first spline member coupled to the primary torque transmitting means and coupled to one of the driving and driven shafts, a second spline member coupled to the primary torque transmitting means and coupled to the other of the driving and driven shafts, the first and second spline members being in mating relation, with the respective splines thereof being disengaged so that the redundant torque transmitting means is inoperative when the primary torque transmitting means is operative, and one of the first and second spline members being displaced upon a failure of the primary torque transmitting means, whereupon said means is rendered inoperative so that the respective splines of the first and second spline members are engaged and the redundant torque transmitting means is rendered operative;   the one spline member having a first main torque transmitting section and a second relatively thin section secured to the first section, and an insulating member separating the first and second sections so that an open electrical circuit through the one and the other of the first and second spline members and the primary torque transmitting means is provided when the redundant torque transmitting means is inoperative, with said circuit being closed through the engagement of the respective splines of the first and second spline members when the redundant torque transmitting means is operative;   a transformer circuit arranged with the redundant torque transmitting means and including a stationary winding, means for exciting the stationary winding and a winding inductively coupled to the stationary winding and rotating with the drive shaft;   the operative redundant torques transmitting means affecting the transformer circuit for short circuiting the rotating winding; and   means connected to the transformer circuit for sensing the short circuit which is indicative of a failure of the primary torque transmitting means.   
     
     
       2. Drive shaft apparatus as described by claim 1, wherein: the closing of the circuit through the engagement of the respective splines of the first and second spline members short circuits the rotating winding which reduces the impedance of the stationary winding; and   the means for sensing the short circuit which is indicative of a failure of the primary torque transmitting means senses the reduced impedance of the stationary winding.   
     
     
       3. Drive shaft apparatus as described by claim 1, wherein: the stationary winding includes first and second portions;   the rotating winding includes a first portion inductively coupled to the first portion of the stationary winding and a second portion inductively coupled to the second portion of the stationary winding;   the first and second portions of the rotating winding are connected in a parallel arrangement;   the first portion of the stationary winding is energized by the energizing means, whereupon a signal is induced in the first portion of the rotating winding;   the second portion of the rotating winding is energized by the signal induced in the first portion of the rotating winding, whereupon a signal is induced in the second portion of the stationary winding;   the closing of the circuit through the engagement of the respective splines of the first and second spline members short circuits the first and second portions of the rotating winding which results in the absence of the signal induced in the second portion of the stationary winding; and   the means for sensing the short circuit which is indicative of a failure of the primary torque transmitting means senses the absence of said signal.   
     
     
       4. Drive shaft apparatus as described by claim 3, including: switching means connecting the energizing means to the first portion of the stationary winding and manually operable to disconnect the energizing means and said winding for testing the transformer circuit.   
     
     
       5. Drive shaft apparatus as described by claim 2, wherein the means connected to the transformer circuit for sensing the short circuiting includes: indicating means connected intermediate the stationary winding and the exciting means and responsive to the reduced impedance of the stationary winding for providing a failure indication.   
     
     
       6. Drive shaft apparatus as described by claim 3, wherein the means connected to the transformer circuit for sensing the short circuiting includes: indicating means connected to the second portion of the stationary winding for sensing the absence of said signal to provide a failure indication.